Rapid Voltage Changes Research Articles

Changes in Farm Supply Voltage Caused by Switching Operations at a Wind Turbine

Renewable electricity sources are now widely used worldwide. Currently, the most common sources are those that use energy contained in biomass, water, sun, and wind. When connected to a medium-voltage grid, individual wind power plants must meet specific conditions to maintain electricity quality. This article presents field study results on the impact of switching operations (turning the power plant on and off) at a 2 MW Vestas V90 wind turbine on the voltage parameters at the connection point of a farm located 450 m from the source. The analysis showed that the wind turbine under study significantly affects customers’ voltage near the source, causing it to increase by approximately 2.5%. Sudden cessation of generation during the afternoon peak causes a 3% voltage fluctuation, potentially affecting equipment sensitive to rapid voltage changes.

Calibration of a Virtual Instrument for Power Quality Monitoring

The paper describes a virtual instrument for power quality monitoring based on NI LabVIEW™ platform and simultaneous measurements of electrical voltages and currents. The virtual power quality analyzer is realized by using National Instruments 9225 and 9227 modules for voltage and current measurements, respectively, NI cDAQ 9174, 4 slot USB chassis and a PC. The created virtual instrument measures power quality characteristics: power frequency, voltage variations, magnitude of rapid voltage changes, flicker severity, voltage unbalance, total harmonic distortion, as well as the elements of voltage dips, short interruptions, and long interruptions defined in the standard EN 50160 for voltage characteristics of supplied electricity. The measurement is according to the general guide on harmonics and interharmonics measurements IEC 61000-4-7. The calibration and verification of the power quality analyzer is a complex task and it is performed by using the laboratory calibrator FLUKE 5500A. The results of calibration and verification of the developed virtual instrument, as well as the results of power quality measurements near different lightning technologies are presented

Enhancing Grid-Forming Converters Control in Hybrid AC/DC Microgrids Using Bidirectional Virtual Inertia Support

This paper presents a new grid-forming strategy for hybrid AC/DC microgrids using bidirectional virtual inertia support designed to address weak grid conditions. The stability of hybrid AC/DC microgrids heavily relies on the AC mains frequency and the DC-link voltage, and deviations in these factors can lead to undesirable outcomes such as load curtailments and power system congestions and blackouts. This paper introduces a unique approach that leverages bidirectional virtual inertia support to enhance the stability and reliability of hybrid AC/DC microgrids under weak grid conditions. The proposed strategy employs virtual inertia as a buffer to mitigate rapid changes in DC-link voltage and AC frequency, thereby enhancing system stability margins. This strategy significantly contributes to a more stable and reliable grid operation by reducing voltage and frequency fluctuations. A standard hybrid AC/DC microgrid configuration is used to implement the bidirectional virtual inertia support, where a bidirectional interlinking converter control is adjusted to deliver inertia support to both the AC and DC subgrids. This converter utilizes the DC grid voltage and AC grid frequency as inputs, effectively managing active power balance and implementing auxiliary functions. Extensive simulations are conducted under weak grid conditions and standalone mode to validate the effectiveness of the proposed strategy. The simulation results demonstrate a remarkable improvement in frequency nadir, rate-of-change-of-frequency (RoCoF), and DC bus voltage deviation in the hybrid AC/DC microgrids. The bidirectional virtual inertia support substantially reduces voltage and frequency fluctuations, enhancing the microgrid stability and resilience. There is an improvement of over 45% and 25% in the frequency deviation and voltage deviation, respectively, achieved through implementing the proposed control strategy.

A one-dimensional model for Pt degradation and precipitation in proton exchange membrane fuel cell considering Pt nucleation, particle size growth, and band formation

Reducing Pt catalysts amount without sacrificing the performance and durability is critical for the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt degradation in the cathode catalyst layer (CCL) decreases the electrochemically active surface area (ECSA), and Pt precipitation, especially Pt band formation, has a significant effect on proton exchange membrane (PEM) stability, resulting in severe PEMFC degradation during long-term operation. In this study, a one-dimensional model is developed focusing on Pt catalyst degradation and precipitation, including Ostwald-ripening, mass loss, precipitation in the PEM from nucleation, particle size growth, to Pt band formation. The model accuracy is comprehensively validated against the corresponding experimental data, including ECSA loss and particle size distribution (PSD) evolution in the CCL under different operating conditions (temperature, relative humidity, and loading mode), as well as the precipitated Pt size distribution characteristics and local potential in the PEM. Using this model, the Pt band formation process is comprehensively analyzed, and the effects of operating conditions on Pt degradation and Pt band formation are investigated in detail. It is found that the nucleation stage is brief, and then the significant inhomogeneity at the size growth stage causes Pt band formation. In addition, the high activation enthalpy of dissolution under low humidity can effectively inhibit Pt degradation, and Ostwald-ripening is the mean cause of Pt degradation, which is likely to occur during the rapid voltage change period.

Numerical simulation of the distribution of reverse currents in a practical alkaline water electrolysis stack immediately after electrolysis

In alkaline water electrolysis, reverse currents are reported to occur after rapid cell voltage change due to the electrodes oxidation state difference and such currents lead to electrodes degradation. The reverse current problems can be more severe in practical applications with larger electrode sizes and larger numbers of cells. In this study, reverse current with changes in the oxidation state of electrodes and potential distribution after sudden shutdown were analyzed based on a multi-physical simulation considering an electronic and ionic conduction in practical-scale. The effects of stack height, number of cells, and ionic resistance through the manifold on the reverse current distribution were investigated. The numerical results reveal that, especially under the condition of low manifold resistance and higher stack height, the discharge current extremely concentrated near the bottom of the edge electrode. This information is important for future stack development because this current concentration can cause severe stack degradation.

Gate Driver Circuit with All-Magnetic Isolation for Cascode-Connected SiC JFETs in a Three-Level T-Type Bridge-Leg

This article presents a gate driver circuit with all-magnetic isolation for driving silicon carbide (SiC) power devices in a three-level T-type bridge-leg. Gate driver circuitry for SiC devices has to be tolerant of rapid common-mode voltage changes. With respect to the resultant potentially problematic common-mode current paths, an arrangement of transformers is proposed for supplying the power devices with drive signals and power for their local floating gate driver circuits. The high-frequency carrier phase-switching technique is used to reduce the number of transformers. Signal timing and other implementation issues are addressed when using this arrangement with the T-type converter. The circuit is demonstrated in a 540 V bridge-leg constructed around 650 V and 1200 V cascode-connected normally-on SiC junction field effect transistors (JFETs).

Дослідження ефективності схеми керування напругою конденсатора уніфікованого регулятора якості електроенергії для зменшення коливань напруги

This article investigated the effectiveness of using a unified power quality regulator (UPQR) to reduce voltage fluctuations in electrical networks with a rapidly changing nonlinear load. It is proposed to use a voltage control scheme on the URYAE storage capacitor based on an FIR filter in order to minimize rapid voltage changes and the flicker indicator, as well as the total coefficient of harmonic distortions in the distribution system. The final simulation of the study is carried out using MATLAB/Simulink. To demonstrate the effectiveness of the proposed control scheme, a comparison of simulation results with a PI controller is made from the point of view of improving the specified power quality indicators. The initial data for performing calculations of voltage fluctuations are information on the parameters of the electrical network and the graph of a random, rapidly changing electrical load. Rapidly changing loads cause rapid changes in the network voltage, the amplitudes of which can reach unacceptable values, for example, in the case of frequent start-ups of an asynchronous motor with a large starting current. Voltage fluctuations can also be caused by technological installations, the operation of which is accompanied by active and reactive power surges , such as the drive of reversible rolling mills, arc steel melting furnaces, contact electric welding installations, etc. The main task of the research is to improve the quality of electricity, and, as a result, to increase the service life of electrical equipment and to ensure the conditions for the normal technological process of electricity consumers. Indicators characterizing voltage fluctuations were quantified: voltage change range (δUt) and flicker indicator (Pt). The effectiveness of the new capacitor voltage control scheme for reducing higher current harmonics compared to the classical one based on the PI-regulator is verified.

Introduction of state-of-the-art low-voltage distribution network devices

Trends towards the development of distributed generation involve a number of problems related to maintaining the quality of electric energy in medium and, especially, low-voltage networks. The article examines the impact of monitoring the quality of electricity of low voltage classes on the reliability of the electrical network. MSZ EN 50160 and Hungarian Energy and Utilities Regulatory Office (MEKH) standards are considered. In accordance with MSZ EN 50160, the main indicators of the quality of electric energy are considered, such as: frequency, voltage fluctuations, rapid voltage changes, Flicker dose, voltage dips, short-term voltage interruptions, long voltage interruptions, temporary overvoltages of industrial frequency, transient overvoltages between current-carrying conductors and voltage ground , harmonic voltage fluctuations, interharmonic voltage fluctuations. SAIFI and SAIDI are calculated according to the Hungarian Energy and Utilities Regulatory Office. The devices for monitoring the quality of electricity of low-voltage networks are analyzed. The factors affecting the choice of the place of installation of monitoring devices are considered. It is presented how power quality monitoring systems can reduce the number of malfunctions in the 0.4 kV network, and the influence of monitoring systems on the quality of electric power in 6-35 kV networks is considered.

Electrical detection and current control of all-optical magnetization switching in GdFeCo ferrimagnetic alloy thin film

We experimentally demonstrated electrical detection of all-optical magnetization switching (AOS) induced by a single femtosecond laser pulse irradiation by measuring alternate rapid changes in anomalous Hall voltage and magneto-optic image pulse by pulse in a Hall-cross shape ferrimagnetic GdFeCo alloy thin film. We also demonstrated that the amplitude of the change in anomalous Hall voltage depended on the position of the AOS-created magnetic domain on the Hall cross. Furthermore, the AOS-created magnetic domains were stable against subsequent current applications in the Hall cross circuit, whereas reversed magnetic domains were not created when the laser pulse was irradiated with a high current. We found that the cooperative effect among magnetism, light, and electric current was assumed to have effects on the absence of the AOS. Combining the AOS phenomenon and electrical measurement/control techniques can realize ultrafast, deterministic, and distinguishable applications.

Experimental evaluation of type‐2 fuzzy logic controller adapted to real environmental conditions for maximum power point tracking of solar energy systems

AbstractThe conventional angle of incremental conductance (AIC) method fails to track the maximum power point (MPP) when a rapid change in solar irradiation and/or panel temperature appears because it cannot distinguish between rapid changes in photovoltaic (PV) current and voltage under real environmental conditions. The present study describes setbacks of the conventional AIC method and proposes an effective approach based on the combination of AIC and type‐2 fuzzy. The proposed approach offers a significant advantage in terms of maximum power transfer to the load under long‐term weather patterns under which broken clouds appear frequently during a 40‐m testing period. The proposed approach is installed on 250 W module of a 10 kWp real PV plant in Kahramanmaras Sutcu Imam University. Later, its performance is validated by dSPACE1104 controller card operating in real time with MATLAB/Simulink tools using daily measured data. The experimental results obtained from the laboratory setup based on dSPACE1104 controller card demonstrate the facility and feasibility of the proposed approach for real PV plant with boost power converter and load.

Low-Frequency Oscillation Analysis of Virtual-Inertia-Controlled DC Microgrids Based on Multi-Timescale Impedance Model

Virtual inertia and damping control (VIDC) improves the stability of DC microgrid (DC-MG). However, the potential positive feedback aggravates low-frequency oscillation induced by the interaction insides control loops, which is explained and solved in this paper. The multi-timescale impedance modelling framework is established to clarify stability mechanism of VIDC and the low-frequency oscillation of VIDC controlled DC-MG. Control loops of different timescales are visualized as independent <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">loop virtual impedance</i> (LVI) elements to form an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">impedance circuit</i> considering the constant power load (CPL), rather than an all-in-one impedance as the external dynamic representation of power converters. Concrete impedance analysis is performed on LVI to reveal the impedance-shaping effect of control loops intuitively, the physical impedance nature of control parameters and the interaction among different timescale, which illustrates the stability mechanism of VIDC. The low-frequency oscillation ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> impedance interaction) in voltage- and inertia-loop is elaborated by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RLC</i> circuits of LVIs. The potential instability factors, resulting in poor damping against voltage oscillation, are also revealed. Thus, dynamic stability enhancement method is further proposed to compensate for the negative damping caused by positive feedbacks of VIDC and CPL, and super-capacitor is added to alleviate rapid voltage changes. Accordingly, the passivity property of system impedance is strengthened and the stability can be evaluated by Nyquist plot. Finally, the simulation and experiment results have validated the low-frequency oscillation analysis and stability enhancement method.

Identification of the flicker source in the power supply systems

THE PURPOSE. To consider issues related to the study of methods for determining the sources of violations of the quality of electrical energy in power supply systems, in particular consumers which create rapid voltage changes or voltage fluctuations that create rapid changes in the luminous flux in electric lighting installations. Show that electrical receivers with a sharply variable operating mode are sources of fluctuations in the consumed current and voltage in the electrical network of power supply systems, which in turn manifests itself in the form of unacceptable values of one of the indicators of the quality of electricity - flicker, defined as the subjective perception of fluctuations in the luminous flux of lighting devices. To study the possibilities of determining the places of occurrence of significant voltage fluctuations without the use of expensive and complex instruments for measuring flicker values in the electrical network. To develop a simplified method for determining the locations of electricity consumers that negatively affect the operation of electric lighting systems and, ultimately, the vision of personnel. Conduct a check on a computer model of a simplified method for determining the places of occurrence of voltage fluctuations that are inadmissible in their magnitude, which are expressed in the appearance of significant doses of flicker that exceed the standard values.METHODS. Solving the problem, a computer model was used, created in the Simulink extension package of the Matlab scientific and technical calculation system.RESULTS. The article describes the relevance of the problem, discusses the quality of electricity in power supply systems. It has been shown using experimental data that in electrical networks there is an excess of the standard values of flicker doses. The possibility of using interharmonic components of the mains voltage to determine the sources of unacceptable doses of flicker is considered. A simplified method for finding flicker sources based on obtaining the values of the derivatives of currents at various points of the electrical network is presented. Computer simulation of an electrical network diagram with electrical receivers, which have both calm and sharply variable nature of work, has been performed. It is shown that the use of the values of the derivatives of the current at various points of the electrical network makes it possible to identify the sources of the occurrence of unacceptable doses of flicker.CONCLUSION. The occurrence of significant rapid voltage changes in the electrical network negatively affects vision, which is inevitably accompanied by increased personnel fatigue and can lead to industrial injuries. The results obtained by the authors of the article show that it is possible to use it to determine the places of occurrence of large voltage fluctuations, which are manifested in unacceptable doses of flicker of the derivatives of currents. It should be taken into account when conducting surveys of power supply systems in order to use fairly simple hardware to identify sources of disturbance in the quality of electrical energy.

An Advanced Modulation Technique Featuring Common Mode Voltage Suppression for Three-Phase Neutral Point Clamped Back to Back Converters

Three-phase back-to-back converters are widely applied in various industrial, commercial, and domestic applications, such as AC motor drives. Due to the non-sinusoidal voltages they generate, a common mode voltage (CMV) appears, leading to problems in electrical drive systems and high-frequency applications. The CMV and rapid voltage changes can cause serious problems, including leakage currents flowing through the parasitic capacitors inside the motor, electromagnetic interference, shaft voltage, and bearing currents that reduce the motor’s lifespan. In general, research to reduce these effects is divided into two methods: modifying the drive system’s physical structure or improving the inverter’s control algorithm. Pulse Width Modulation (PWM) methods are commonly used in control algorithms of converters to reduce the CMV. However, adding pulse amplitude modulation to the PWM helps reduce the CMV. The technique of simultaneous pulse width and amplitude modulation of space vectors is proposed in this paper to reduce the CMV and its destructive effects in drive systems. The proposed technique is based on the elimination of zero vectors and the inherent reduction of DC link voltage by amplitude modulation leading to a further reduction of the CMV; The obtained results of applying the proposed strategy to a three-phase back-to-back NPC converter with 738-watt steady-state operating point power showed the system’s sufficient behavior with the efficiency of 98.62 percent. Finally, the transient performance of the converter from no-load to full-load condition ensures its sufficient behavior for industrial applications.

PV based DG Power Quality Improvement Using Integrated D-STATCOM under varying Insolation

Abstract: The standalone grid connected Photovoltaic (PV) systems have been gradually increasing for generation of electrical energy due to ever increasing fuel and coal prices, as well as the environmental issues posed by conventional power plants. In this transition phase, power quality is at its expense, resulting in damage to equipment or appliances and lost in production. Inadequate power quality can be caused by network failures and switching operations, which primarily cause voltage dips, interruptions, transients, and network disturbances from loads which primarily produce flicker i.e., rapid voltage changes, harmonics and phase imbalance. In this paper PV is used as an external DC source for D-STATCOM (Distributed Static Synchronous Compensator) which is a FACTS device that can maintain and repair power quality limitations such as power factor correction, voltage control, load balancing and harmonic reduction. The PV-STATCOM system inverter is implemented by impending MPPT method using P&amp;O algorithm so as to provide DC link voltage control and to improve transient response along with counteracting power quality issues. MATLAB/Simulink based simulation results are presented for the proposed PVSTATCOM model. The simulation results proves that the PV-STATCOM system has better Total Harmonic Distortion (THD) and good reactive power compensation at different irradiance levels. Keywords: Photovoltaic (PV) systems, D-STATCOM (Distributed Static Synchronous Compensator), Total Harmonic Distortion (THD), MPPT (Maximum Power Point Tracking), FACTS (Flexible AC Transmission System)

Analysis of Network Impacts of Frequency Containment Provided by Domestic-Scale Devices Using Matrix Factorization

This paper studies the distribution network impacts of frequency containment services derived from domestic-scale devices. Risk metrics considering the likelihood and severity of violations are proposed, given uncertainty in the location of these devices. A novel linearization approach is proposed to enable detailed simulations of large-scale networks, capturing MV–LV coupling in European-style networks of over 100 000 nodes. The approach combines a novel factorization of the power flow Jacobian matrix and an efficient linearization update step. The first of these innovations improves the scalability and practicality of the linearization, reducing the memory and computational requirements by as much as twenty times, whilst the latter reduces the median linearization error by at least 50% in all networks studied. It is demonstrated that rapid voltage change (RVC) and overvoltage constraints could limit the uptake of these devices to just a fraction of one percent of customers if the response is not managed. Sensitivity analysis demonstrates that both the likelihood and severity of constraint violations increases rapidly with the size of the devices used for frequency response.

Improving the Detection of RVCs for a Better Assessment of Their Influence on Flicker

Rapid Voltage Changes (RVC) produce sudden illuminance changes that can generate flicker. The IEC 61&#x00A0;000-4-30 standard defines the procedure for the measurement of RVCs, but it does not include a metric to assess the effect of RVCs on the perception of flicker. The IEC 61&#x00A0;000-4-15 standard establishes the specification of a flickermeter, which assesses the effect of voltage fluctuations on flicker by calculating the flicker severity, <inline-formula><tex-math notation="LaTeX">$P_\text{st}$</tex-math></inline-formula>, during a 10&#x00A0;min interval. However, <inline-formula><tex-math notation="LaTeX">$P_\text{st}$</tex-math></inline-formula> is ineffective to adequately assess voltage variations as fast and short as RVCs. This work analyzes the main characteristics of the RVCs affecting flicker. The relationship between the amplitude and rate of change of the RVC and the instantaneous flicker perception, <inline-formula><tex-math notation="LaTeX">$P_\text{inst}$</tex-math></inline-formula>, during the event is quantified. A method to estimate the amplitude of RVCs, and consequently to detect them, is proposed. The method is based on the maximum variation and rising slope of <inline-formula><tex-math notation="LaTeX">$P_\text{inst}$</tex-math></inline-formula>. The model is tested on 576 hours of recordings from five different low voltage locations. It provides high precision, with a mean deviation below 0.2&#x0025; in the RVC estimated amplitude. This method could be used by the IEC flickermeter to define a more precise and complete strategy to address the flicker assessment.

Modelling of distribution level coreless induction furnace for rapid voltage change assessment

This paper proposes a mathematical model for a distribution level, directly fed core-less, induction furnace that can be used for network voltage behavior related studies performed by the network operators. The objective of the model is to represent the dynamic behaviour of the facility when an induction furnace is energized (switched) at the beginning of the melting process. Model development is supported by actual field measurements from PCC to a distribution system. The paper includes a case study and the results indicate that the proposed model offers accurate results for rapid voltage change assessment and it is shown that the model can be successfully used for various load changes and at various voltage levels.

Characterization of the impact of PV and EV induced voltage variations on LED lamps in a low voltage installation

Photovoltaic (PV) systems, Electric vehicles (EV) and LED lamps have gained significant popularity in our current society. It is therefore common to find customer installations with all three operating together. PV and EV are known sources of voltage variations on the grid. The impact of these voltage variations on LED lamps situated in close proximity to PV or EV in a low voltage installation, in terms of overvoltage, undervoltage, and rapid voltage changes is systematically studied in a laboratory environment in this paper. Such variations can cause malfunctioning of the lamp based on its immunity and tolerance level or be disturbing to the end-user based on the intensity of variations and rate of recurrence of being subjected to such variations. In this work, the observed impacts on LED lamps are illustrated as 15 different cases. The scope of this work is to identify the possible impacts due to voltage variations induced by PV and EV systems on LED lamps and the potential problems that could happen long term due to recurrent subjection of such voltage variations.

Estimation of Parameters Associated With Individual Sources of Voltage Fluctuations

The paper presents research results on a novel algorithm that allows estimation of parameters associated with the specific voltage fluctuation sources in the power grid, which change their operating state with a frequency of up to 150 Hz. The proposed algorithm allows estimating the rate of changes of the disturbing load state, the amplitude, and shape of voltage changes caused by specific sources of disturbances. The decomposition of the estimated AM modulation voltage signal in the power grid is used to implement the algorithm. The algorithm uses a carrier function estimator, which allows research on disturbing loads that change their operating state with a frequency greater than the power frequency. The enhanced empirical wavelet transform is used for the decomposition, which allows recreating the selected parameters, considering random operation of disturbing loads. Accurate recreation of selected parameters will allow selective location of disturbing loads by assessing the propagation of voltage fluctuations caused by specific sources of disturbances. An alternative algorithm has been proposed with coding of voltage changes to voltage fluctuation indices determined from the estimated AM modulation signal of voltage, allowing reducing the necessary memory of the measuring device. Experimental studies have been conducted for the proposed algorithms, considering rapid voltage changes.

Quantification of Voltage Profiles Intermittency for Small-Scale Solar Photovoltaic System under Different Loading Conditions

The recent rapid uptake of solar photovoltaic system in Malaysia has introduced new challenges to the operation of the power grid, particularly on the voltage profile of distribution networks. An intermittent nature of the voltage fluctuation that caused by solar output remain as important topic as how these rapid voltage changes will affect the operation of the network. Hence, this paper presents a quantification of voltage profiles intermittency for small-scale solar photovoltaic system under different loading conditions. Actual field measurements have been performed for both high and low loading conditions. Mainly two parameters have been analysed for this work, namely voltage profile and solar power output. An intermittency quantity of voltage profile during solar generation for day time is higher than night time, which indicates high intermittent in solar irradiance causing rapid fluctuation in solar generation. Furthermore, increased voltage magnitude was observed during the low load condition. The high voltage intermittency caused by rapid fluctuation of solar output and voltage rise during low load giving a negative effect on distribution network. It is expected that grid-connected battery energy storage system could serve as the potential solution to alleviate both solar intermittency and voltage raise issues.